Endosomal compartments have diverse functions. In addition to their classic role in delivering internalized cargo to lysosomes for nutritional purposes and for the down- regulation of cell surface receptors, they also serve to direct biosynthetic cargo to a diverse set of lysosome-related organelles. The regulation of endocytic trafficking is also closely linked to autophagy which constitutes a second delivery pathway to lysosomes. This pathway accomplishes the engulfment of intracellular components into autophagosomes which ultimately fuse with lysosomes to degrade their content. Autophagy may be the most important defense cells have against the accumulation of damaged and aggregated proteins and dysfunctional organelles. Interference with autophagy hastens degenerative processes in the eye or other tissues and has also been linked to cancer. Drosophila constitutes an excellent model system to analyze a novel pathway that links the regulation of autophagy to that of endocytic trafficking. The dAcinus protein modulates endocytic trafficking and enhances signaling by the EGF and Notch receptors. DAcinus is also necessary for the normal maturation of autophagosomes whereas increased levels of dAcinus induce autophagy. Aim 1 proposes to use genetic and transgenic approaches to determine which extracellular signals are responsible for the different aspects of the dynamic regulation of dAcinus in the developing eye. Aim 2 will analyze which elements within the dAcinus protein mediate its regulation in the context of endocytic trafficking and autophagy. Aim 3 will determine which targets in endocytic trafficking and autophagy are regulated by dAcinus function using a combination of next generation sequencing and genetic approaches. PUBLIC HEALTH RELEVANCE: Autophagy is a mechanism by which cells encase a subset of themselves into a membranous compartment and subsequently deliver its content to lysosomes for degradation and eventual reuse of the individual building blocks. The specific aims described in this proposal will investigate a novel mechanism that allows the induction of autophagy in cells and links its regulation to the exchange of developmental signals between cells. This work is important for human health, as we know that the proper level of autophagy is critical when a cell is stressed by the early effects of neurodegeneration, starvation and also in the context of cancer.